My worst experience with a contractor: The roofer removed the old roof when the forecast was for rain. It rained and water came in all over the interior and stained the ceiling. During the installation, the roofer damaged the interior ceiling; pounded nails that were too long that went through the ceiling; broke skylights; and the skylight framing miter corners had gaps up to one inch. The roofers nearly drove nails into the electrical until I stopped them. The manager was reluctant to show up to the job site so I had to supervise. The roofer prepared an invoice with a 5% bonus even though he missed the agreed completion date and did less work scope than originally agreed. The first rain after the roof installation, the roof leaked in no less than twenty locations. It was worse than the old roof that had only two small leaks.
Cons: Poor worksmanship, No site management, Questionable ethics